This anthology discusses questions from a philosophical and didactic perspective, such as: What does it mean to understand a mathematical concept? How does understanding of mathematics develop in the learning process? How can we understand mathematics education? Ultimately, how can mathematics as a whole be understood, and what does such understanding contribute to human understanding in general? The book promotes a broad discussion about mathematics and its significance for the public; it reflects on the self-understanding of mathematics, its relationship to the world, and questions regarding the meaning of mathematical activity. The selected and referenced contributions for the book come from experts in the field of mathematics education and philosophy, and they were discussed internationally and interdisciplinary at a conference.